1. Field
The present disclosure relates to a display device, and particularly to an organic light emitting display device.
2. Description of the Related Technology
Recently, flat panel displays that have a light weight and a slim profile have drawn attention as next generation displays. Examples of such flat panel displays are a plasma display panel (PDP), a liquid crystal display (LCD), and an organic light emitting display.
Because organic light emitting displays are a self-light-emitting type which displays an image by inducing an organic compound to emit light, they have a wide viewing angle and high resolution, compared to other flat panel displays. Organic light emitting displays can be categorized into an active matrix (AM) type and a passive matrix (PM) type depending on the driving methods.
Organic light emitting displays include an array of pixels for displaying images. In the AM-type organic light emitting display, each pixel typically includes a light emitting unit configured to emit light and a circuit unit configured to drive the light emitting unit. Because of having diode characteristics, the light emitting unit is referred to as an organic light emitting diode (OLED). The light emitting unit includes an anode (hole injection electrode), a cathode (electron injection electrode), and an organic layer interposed therebetween.
The circuit unit typically includes two thin film transistors (TFTs) and one capacitor. One of the two thin film transistors serves as a switch for selecting the organic light emitting layer of a pixel to emit light among a plurality of pixels. The other thin film transistor serves as a driving element for applying a driving power source for driving the light emitting layer of a selected light emitting unit to emit light.
Certain organic light emitting displays are configured to emit light through the cathode(s) of the light emitting units. Such organic light emitting displays are generally referred to as a front light emitting type. In such organic light emitting displays, the anodes of light emitting units are connected to the drain electrodes of thin film transistors. Each of the anodes can be a single-layered reflective electrode or a multi-layered electrode including a reflective electrode.
A reflective electrode is typically formed using an etching process. In forming a reflective electrode, a reflective material is deposited and then is patterned to form isolated portions for individual pixels. Thus, a large portion of the deposited reflective material is etched away. During the etching process, many particles of the reflective material or impurities can be produced. Because the particles may remain and form dark portions in the reflective electrode, the organic light emitting display may have defects.
The above information disclosed in this Background section is only for furthering the understanding of the background of this disclosure and it may contain information that does not constitute the prior art.